Gonna try a dashpot

[Patrick62]

Ok, let me explain the situation. It's the log splitter with the 18hp v twin engine on it running a 22 gpm pump.
It runs fine, but surges... when loaded. This puzzled me for a year or two, and then last year I came upon a work around.
I crank up the idle screw to about the same rpm as the engine is running. Ok, that answered questions.
Slam it into reverse, and there is a little more load on the engine, and it throttles up. Over shoots the speed a bunch, governor drops to closed, and then it is too slow, and it goes back to way too much. Irritating. Worse when oil is cold. Almost normal when oil is all the way up to hot. Cranking the idle screw up to hold the throttle at about RPM keeps it from dropping out while governor figures out where it wants to be. Blessed smoothness.
Yesterday, I was watching this thing doing it's surge, and remembered that some car engines had a dashpot to keep the throttle from closing rapidly. This just might be the ticket!
Set it up on the governor arm as a damper. Ordered one from ebay, and with a little linkage I can try it

Think it will work?

 

[Del_]

It sounds like you need a carb rebuild.

My 18hp briggs IC drives a 28gpm 2 speed pump and would stall on heavy sudden loading. When I replace the carb gasket I found that it had failed and was letting two sections of the carb bleed into each other. The gasket fixed it and that was 5 or 6 years ago. Still working fine.

 

[Patrick62]

It works a charm!
Took me two tries to get the bracket the right size, shape.
Started her up, and that usually results in surging. Nope, settled right to speed.
Flip the lever for high speed, and this would always result in surging. Nope, settled right to speed.
Split a block of wood, and hit return... this is the acid test here. It would ALWAYS do the hunt and seek
brap, brap, brap, brap.... for like even 10 seconds after the cylinder completes it's return.
It returned, smooth. speed stayed reasonable... Ka-*****.... Purrrrrrr.....


18HP Briggs V twin is massive overkill for a 22 gpm 2 stage pump. So, the governor is sensitive enough that when the engine sees a load, it throttles up. Oh Boy! does it throttle up. Over speed condition. Governor drops carburetor to closed. Underspeed, and then the governor slams the throttle back open.... Repeat. repeat. until it finally settles down.
Having spent many many hours with this machine, lots of thought process. The quick fix was just crank up the idle screw to keep the carby from closing all the way. It worked. However... pain to have to keep re-adjusting the idle screw, go to shut it down, and have to loosen the screw to idle it down, you know the deal.
Then... I remembered dashpot's
THis morning I had a even more hair brained idea, a shock absorber for a RC toy car.... !!!

 

[sean donato]

Why not just fix the actual issue? It's either a improperly adjusted govenor or a carb issue. I'm all about creative ideas, but there's an underlying issue here that should be pretty easy to fix and non of that other stuff would be needed.

 

[Patrick62]

I appreciate the feedback, I think this is fixing it right.
Carburetor works fine. Engine will idle along at a low speed of like 1200 or something like that, and I have about 3000 or so for the high speed. When I first got the engine, the governor was not correct from the factory. I considered that a bit strange.
Why is this giant engine slowing down a bunch with that pump? But it split wood, just bugged me a bit.
Eventually after wood season (split a bunch of wood tho) I went after it, and discovered that the linkage was badly adjusted.
Set it up, and got the springs they way it should have been, a idle speed to warm things up, and about 3000 or so for high speed.
I could probably ask it for 3600, but considering a pair of 1/2 inch ports on the cylinder and heating the oil up... 3K is fine. Still gets a bit warm after a couple hours...

It probably would be possible to "rich" the carburetor to where it would bog some, and then it would not surge as much.
I get it, one theory is that the low speed or idle circuit is restricted, or plugged up somehow. I believe I could reduce that idle spring to where this engine would tick over at like 800 or so rpm. I have held the throttle closed, and it will idle along quite nicely.
So, I don't think anything is plugged up.

I am gonna run it awhile with this gizmo on it, and if I am happy with it, what's wrong with that?

 

[sean donato]

With the govenor working properly you don't need any of the stuff you just put on it. It's your engine, you do what you want, but I personally would just fix it.

 

[pdqdl]

I agree. When they surge and over-rev, or drop RPM too much, the governor isn't correctly coupled to the throttle linkage.

That being said, I'm quite interested in seeing a picture or link to your "dashpot". I have no idea what that would be, relative to a carburetor linkage.